Editing Bitboard (section)

==History==
The bitboard method for representing a board game appears to have been invented in the mid-1950s, by Arthur Samuel and was used in his checkers program.<ref name="IBM_1959"/>
For the more complicated game of chess, it appears the method was independently rediscovered later by the [[Kaissa]] team in the [[Soviet Union]] in the late 1960s,<ref name="Ru_1970"/> and again by the authors of the U.S. Northwestern University program "[[Chess (Northwestern University)|Chess]]" in the early 1970s.  The 64-bit word length of 1970s super computers like Amdahl and Cray machines, facilitated the development of bitboard representations which conveniently mapped the 64-squares of the chessboard to bits of a word.

Rotated bitboards for collating the moves of sliding pieces were invented by Professor Robert Hyatt, author of Cray Blitz and Crafty chess engines, sometime in the mid-1990s and shared with the Dark Thought programming team. They were later implemented in Crafty and Dark Thought, but the first published description wasn't until 1997.

A decade later, direct lookup methods using masked ranks, files and diagonals to index a table of attack vectors depending on occupancy states of bits under the mask, were introduced.  One such scheme utilizing a perfect hash function to eliminate hash collisions, was termed "magic bitboards".  Nonetheless, the large size and high access rates of such tables caused memory occupancy and cache contention issues, and weren't necessarily more efficacious than the rotated bitboard approach.
Today, game programs remain divided, with the best scheme being application dependent.